What happens if your software haves 2 binaries that talk to each other and one of them contains the GPL'd code; can I just give the code for that one or do I have to release the source of both?
Sooner or later, laws will get interpreted by a judge/jury. You question is equal to asking at what point a work should be considered a derivative work.
The answer is sadly quite blurry, and country specific. US law say something like: "A “derivative work” is a work based upon one or more preexisting works, such as ... abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted."
What would a judge say about two separate programs that talk to each other? A lot of people and companies has their opinion about it, but there is not much of case law in existence. All one can say is that the GPL author does not consider IPC level of communication to trigger a derivative work.
